Audio files from dedicated server to client on demand

Hi, I’m making an MMO and all dialogues are stored as text server side in the database, so the player cannot just look at the dialogues and figure out the solution of quests, or get information about the next ones. The dialogue text is sent from the dedicated server to the client only when needed through RPC. The problem is that now I would like to add voiceovers to the quests. Voiceovers are audio files, which can be easily extracted from a packaged project by a player (UnrealPak), so if I ship those my game will be spoiled so easily. Is there a way to serve assets on the fly on top of the packaged game? Can I send to the player some voice files only when he runs the quest? Or what is the best way to accomplish this? I read about encrypting Pak files, but this seems to have an impact on performances, and I guess there are anyway ways to hack the pak files.